The most astonishing lesson in physics gained from floating rivers is the inclination of water to reverse direction and flow back into a “hole”. Even in the steepest rapid and in spite of its tremendous weight and momentum, when an obstruction (usually rock or ledge) forces a divergence of flow, that stupid water wants to go back upstream and fill the void. Nature abhors a vacuum.

River folks call these features holes or reversals. They are dangerous features that surviving river runners learn to avoid.

Our planet has a river of Carbon dioxide. We humans produce about 10 gigatons of the stuff each year, but about 200 additional gigatons is outgassed at ocean upwelling zones, and chemically produced by other living things. Of this, about 120 gigatons is used by plants and about 90 gigatons sinks back into the ocean in downwelling zones primarily in the North Atlantic and around Antarctica. All of this in one year.

Well, these downwelling zones where 90 gigatons of Carbon dioxide sink are holes in the Carbon dioxide river, and a surely as water will flow uphill to fill a void, Carbon dioxide will flow to fill these holes.